Elastic Scattering of Protons from CALCIUM-40, CALCIUM-42 and CALCIUM-44 in the Energy Range 20 - 50 Mev, and Nuclear Matter Radii.

Measurements of proton elastic scattering differential cross sections have been made for for the ('40)Ca, ('42)Ca and ('44)Ca isotopic sequence at mean incident energies of 21.0, 25.0, 30.0, 35.0, 40.0, 45.0 and 48.4 MeV. The angular distributions cover the range 10(DEGREES)- 170(DEGREES) (in the laboratory) in 2.5(DEGREES) steps at forward angles and 5(DEGREES) steps at backward angles. The differential cross sections have relative errors of about 3.0% while the scale errors are less than 2.5%. The data have been analyzed in terms of a standard optical potential with an explicit -dependent term. Differences between the r.m.s. radii of the neutron and proton distributions have been deduced and are compared with the results of previous measurements and with various theoretical predictions. In general there is good agreement between the present results and those obtained in analyses of intermediate energy proton and alpha elastic scattering data. The Coulomb displacement energies yield smaller values while pionic atom data yield larger values than those obtained from hadronic scattering data. The predictions of Hartree-Fock calculations are in satisfactory agreement with the hadronic scattering results results whereas the shell-model predictions are too large.